Cell Structure + Cell division- biology paper1

Question 1

What type of cells are bacterial cells?

Answer 1

Prokaryotes

Question 2

Why are microscopes useful?

Answer 2

Because they allow us to see individual cells and their sub-cellular structures, which we wouldn’t be able to see with the naked eye.

Question 3

What are the 2 types of microscope?

Answer 3

Light and electron

Question 4

What do light microscopes do?

Answer 4

They use light and lenses to form an image of a specimen and magnify them. With a light microscope, you can see individual cells and large subcellular structures such as the nucleus.

Question 5

What do electron microscopes do?

Answer 5

They use electrons to form an image. They have a much higher magnification and resolution than light microscopes. So, we can see much smaller things in detail, like the internal structure of mitochondria and chloroplasts. We can even see tinier things like ribosomes and plasmids.

Question 6

What is another name for the resolving power?

Answer 6

The resolution

Question 7

What is the resolution of a light microscope?

Answer 7

around 0.2 μm, or 200 nm. This means that it cannot distinguish two points closer than 200 nm.

Question 8

What are the 2 types of electron microscope?

Answer 8

The scanning electron microscope (SEM) and The transmission electron microscope (TEM)

Question 9

What is the highest magnification of a light microscope?

Answer 9

X 2000

Question 10

What is the highest magnification of an electron microscope?

Answer 10

X 2million

Question 11

What is the resolution of a scanning electron microscope (SEM)?

Answer 11

10nm

Question 12

What is the resolution of a transmission electron microscope (TEM)?

Answer 12

0.1nm

Question 13

What is a field of view?

Answer 13

The area seen when looking through a microscope

Question 14

The SEM microscope…

Answer 14

has a large field of view so can be used to examine the surface structure of specimens. SEMs are often used at lower magnifications.

Question 15

The TEM microscope…

Answer 15

is used to examine thin slices or sections of cells or tissues.

Question 16

What is the magnification of a TEM microscope

Answer 16

X 1 million

Question 17

How do you prepare a slide using a light microscope?

Answer 17

1) Add a drop of water to the middle of a clean slide
2) Cut up some onion and seperate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers
3) Using tweezers, place the epidermal tissue into the water on the slide
4) Add a drop of iodine solution, Iodine solution is a stain. Stains are used to highlight objects in a cell by adding colour to them.
5) Place a cover slip on top. To do this, stand the cover slip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen.

Question 18

What is eosin used for?

Answer 18

Making the cytoplasm show up

Question 19

How do you observe a specimen using a light microscope?

Answer 19

1) Clip the slide you’ve prepared onto the stage
2) Select the lowest-powered objective lens (the one that produces the lowest magnification)
3) Use the course adjustment knob to move the stage up to just below the objective lens.
4) Look down on the eyepiece. Use the course adjustment knob to move the stage downwards until the image is roughly into focus.
5) Adjust the focus with the fine adjustment knob, until you get a clear image of what’s on the slide.
6) If you need to see the slide with greater magnification, swap to a higher-powered objective lens and re-focus.

Question 20

Why do cells differentiate?

Answer 20

Cells differentiate in order to develop their sub-cellular structures so that they can change into different types of cells and carry out specific functions

Question 21

Give 3 ways a sperm cell is adapted to swimming to an egg cell

Answer 21

• The sperm has enzymes in ts head to digest through the cell membrane of the egg
• The sperm has a long tail and a streamlined head to help it swim to the egg faster
• The sperm contains many mitochondria to provide the energy needed for movement

Question 22

Why are nerve cells long

Answer 22

So that they can cover more distance

Question 23

What are embryonic stem cells

Answer 23

Undifferntiated cells found in human embryos. They have the potential to differntiate into any kind of cell at all.

Question 24

Apart from the embryo, where else are stem cells found in the human body

Answer 24

The bone marrow. However, stem cells from the bone marrow can only differentiate into certain cells, like blood cells

Question 25

Where are the stem cells in plants found

Answer 25

The meristems

Question 26

Why are some people opposed to the idea of using human embryos in stem cell research?

Answer 26

Some people think that stem cells are a potential human life.

Question 27

What are chromsones

Answer 27

Coiled up lenghts of DNA molecules.

Question 28

What are genes

Answer 28

Sections of chromones that control the development of different characteristics e.g. hair colour.

Question 29

What is mitosis

Answer 29

Cell division

Question 30

What is the name of the process that bacteria use to divide

Answer 30

Binary fission

Question 31

What is the maximum temperature microorganisms in a school lab can be grown and why?

Answer 31

25 degrees Celsius, otherwise harmful pathogens may be grown uncontrollably

Question 32

How can you make sure the experiment that tests the effect of antibiotics on bacteria is not contamianted

Answer 32

- The petri dishes and culture should be sterilised before use to kill any unwanted microorganisms - The inoculating loop should be sterilised by passing it through a hot flame - After transferring the bacteria, the lid of the petri dish should be lightly taped on - to stop microorganisms from the air from getting in - The petri dish should be stored upside down- to stop drops of condensation falling onto the agar surface.

Question 33

Describe the experiment that tests the effect of antibiotics on bateria

Answer 33

1) Place paper disks soaked in differnt types of antibiotics on an agar plate that has an even covering of bacteria 2) The antibiotics should soak into the agar jelly. Antibiotic-resistant bacteria will continue to grow on the agar areound the paer disks, but non-resistant starins wll die. A clear area will be left where the bacteria have died(inhibition zone). 3) A control should be used- a paper disk that has been soaked insterile water instead of in antibiotics 4) The plate should be left at 25 degrees Celsius for 48hrs. 5 The more effective the antibiotic is against the bacteria, the larger the inhibition zone will be.

Question 34

What is diffusion

Answer 34

The movement of particles from an area of high concentration to an area of low concentration.- down the concentration gradient

Question 35

Name substances that can diffuse through cell mebranes

Answer 35

Oxygen , carbon dioxide, glucose, amino acids, water

Question 36

Name substances that can't diffuse through cell membranes

Answer 36

Starch and proteins

Question 37

What type of molecules move by osmosis

Answer 37

water

Question 38

What are the 2 main differences between active transport and diffusion

Answer 38

Active transport requires energy- diffusion does not During active transport, particles move up the concentration gradient. Whereas they move down the concentration gradient.

Question 39

Describe the steps of the cell cycle

Answer 39

-Growth and replication(interphase) >The DNA is spread out in long strings >The cell grows and increases the amount of sub-cellular structures, such as mitochondria and ribsosmes >The cell replicates its DNA -Mitosis >The chromosnes line up at the centre of the cell and the cell fibres pull them apart. One set of chromosnes is pulled to each end of the cell >Membranes form around each of the sets of chromosnes. These become the nuclei of the 2 new cells(the nuclei have divided) >Lastly, the cytoplasm and the cell membrane divide 2 identical daughter cells have now been produced.

Question 40

Which ways are the villi in the small intestine adapted for the absorption of digested food

Answer 40

- A singe layer of surface cells, short diffusion path | - Surrounded by a network of capillaries and good blood supply, quick absorption

Question 41

What happens to unwanted stem cells from fertility clinics anyways?

Answer 41

They would get destroyed if not used for research so some people argue that they might as well be used

Question 42

What are the advantages of stem cells in plants?

Answer 42

Throughout the plant's entire life, cells in the meristem tissue can differentiate into any type of plant cell.These stem cells could then be used to produce clone of plants quickly and cheaply Consequent, plants of rare species can be grown and crops with desired features could also be grown .

Question 43

What is binary fission?

Answer 43

The process by which prokaryotic bacterial cells divide

Question 44

Describe the steps of binary fission

Answer 44

1) The circular DNA and plasmids replicate 2) The cell gets bigger and circular DNA strands move to opposite ends of the cell 3) The cytoplasm begins to divide and new cell walls begin to form 4) The cytoplasm divides and 2 daughter cells are produced

Question 45

The daughter cells produced through binary fission...

Answer 45

have one copy of the chromomal DNA, but can have a variable number of copies of plasmids